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ElectricSteve writes with this excerpt from Gizmag:
"Ready for a bit of a mental mechanical challenge? Try your hand at understanding how the D-Drive works. Steve Durnin's ingenious new gearbox design is infinitely variable — that is, with your motor running at a constant speed, the D-Drive transmission can smoothly transition from top gear all the way through neutral and into reverse. It doesn't need a clutch, it doesn't use any friction drive components, and the power is always transmitted through strong, reliable gear teeth. In fact, it's a potential revolution in transmission technology."

The real icing on the cake is (as mentioned near the end) the secondary drive doesn't require a whole lot of power so it can be run by a flywheel. Infinite torque? Frictionless? This is almost too good to be true, there has to be some catch. Like the primary input drive requires more energy than they expected but I can't see it--although I'm not a mechanical engineer.

This is the kind of thing you like to see -- I hope this man has all the capital he needs and gets that prototype up and running for demonstrations. Plus it's a small time plumber inventor... these are the kind of news stories an engineer loves to read about.

Well, obviously this is not "frictionless" - it just appears not to use friction as the main force of transmission, like friction-cone type CVTs do. There are other types of CVTs that do not use friction - for example chain-driven CVTs or hydraulic-type CVTs. Theoretical infinite torque is also not exactly new - look at hydristors, for example. I'd love to see more technical detail about what the guy actually invented there, TFA is not exactly helpful when it comes to the inner workings of his gearbox.

It is indeed similar to the planetary gear coupling boxes in parallel hybrids. And yeah, you are basically right - a 6-gear box holds you sufficiently close to the optimum rpm anyway for practical use. CVTs really shine in heavy machinery, but are not that important for personal cars. Still nice technology, though. To hell with practical importance - all hail those engineering efforts done for the heck of it!

It seems that manufacturers don't want to build things that last forever. Planned obsolescence is the current fashion.

Planned obsolescence because of new safety measures, new gadgets on-board and new designs yes. Because of breakdowns, no. Perception in the eyes of buyers about how reliable your brand of cars is, can kill the sales of any car if people think your car breaks down faster than other cars. Toyota sells so many cars precisely because they don't break down (or are perceived as more robust) as US cars. In fact, it's incredibly difficult to sell US made cars in Europe because of exactly this problem. So any car manufacturer who can make his cars more reliable, in whatever way, *while not heavily impacting the manufacturing cost*, will do so.

Planned obsolescence has been around a lot longer than "current fashion".

There is a story about Henry Ford - probably apocryphal, but it has the ring of truth - and the durability of the Model 'T'.Story has it that in the 1920s, Ford sent a number of staff around the US to "beg, steal or borrow" as many scrapped Model 'T's as they could get. He then had each one stripped down and inspected to find out which components were failing and which ones weren't. The guys

This device has a "powered neutral" determined by getting two input shafts spinning at precisely the same speed - otherwise you are moving. You aren't going to manage that manually so you are likely looking at some form of electronic (+ software) implemented "neutral" switch. You'd better be worrying about how long before _that_ goes wrong - because it's going to be fun controlling the car when it does (without a clutch, remember).

Nitpicking: that applies in the US. In a great part of the world it is the contrary. As an example, in France, driving school and driving tests are by default on manuals. If you take the test on an automatic, you get a license saying it is limited to automatics. The times I've bought cars, the dealers never even asked if I'd prefer automatics.

In other news, automatics have reputation of being less fuel-efficient and slow to kick in when you quick acceleration. Maybe that is no longer true, but the reputation sticks.

So the large number of people in the US with a new car fetish who trade them in ever 2-4 years...or those leasing cars who get a new one every 3 years...will be forced to...what?

Cars are already far more reliable than they were 15 years ago and manufacturers strive for increasing reliability because it's a key selling point...even though people often don't keep the car long enough for it to matter. If you made the a car nearly service free for 5 years then you can sell include "free service" for 5 years wi

Not for windmills, generators and the like, keeping those at a constant RPM can be more useful independant of input power. It may also prove useful in electric cars, as if you can keep everything always working at it's peak efficiency you can go further on less power. There are many situations where it would be better to have a constant RPM in and a variable out (or vice versa), the question then becomes are these as easy to work with and reliable as existing gearboxes. Planetary gears, work at approximately the maximum efficiency most of the time, these theoretically can work at maximum efficiency ALL of the time.

If they can be a drop in replacement for existing tech, then I can see this taking off, if not or they require complex setups/electronics it might be a more niche product. Also how efficient this tech is, in comparison with existing systems, as if the gearbox itself is only 75% efficient, this would rule out the benefit of having an infinietly variable ratio. Pulling some numbers out of my ass I believe gearboxes are some where in the 95-99% efficient

Actually, the transmission in the Prius is completely different from this. The Prius takes two full power inputs (the engine and the electric motor), and adjusts the power output from the two (balancing them) to achieve the end ratio. This takes a single full power input (and two factional inputs, perhaps a very small fraction if friction losses are small enough), and produces a variable end ratio. Quite a big difference between them. For the Prius transmission to work, both engines need to be of comparable power (A 100 hp gas engine would need somewhere near a 100hp electric motor). This would likely work with a 100hp engine and a pair of 1/2 hp (or less, depending on precision and friction) electric motors.

And FYI, an OTTO cycle engine is not most efficient at 2000 rpm. It's most efficient at its horse power peak RPM, and at full throttle. Anything less than that (RPM or throttle), and you lose volumetric efficiency. And when I say efficient, I'm saying the power/fuel use is the maximum. It's all about the intake and exhaust design (you can tune them for maximum efficiency at a particular RPM for a particular engine design). That's why hybrids typically use smaller engines. So that you can run it closer to its peak power for longer (40hp at full throttle would be plenty to cruise on the highway and still be able to charge the batteries without needing to be throttled back).

No, the most efficient point is at peak torque. That's where the engine is able to produce the most energy for a given amount of gas. The horsepower peak is where the engine is producing the most power (energy/time). It is not necessarily it's most efficient point unless they coincide which is rare.

You've got the volumetric efficiency relative to rpm part backwards. Volumetric efficiency goes down with rpm. Thermal losses go up as surface area of cylinder goes up. However, pumping losses etc go up with rpm. So, the most efficient engine is one that is able to produce the most torque out of the smallest displacement. Or in other words, run at the lowest rpm to meet application's power needs. This is what lies at the heart of why you see in countries where fuel is more expensive than in the US the

You've got the volumetric efficiency relative to rpm part backwards. Volumetric efficiency goes down with rpm.

Not true. Volumetric efficiency is measured as the the volume of air taken in on each stroke vs the displacement of the cylinder. So if 1 liter of STP (Standard Temperature and Pressure) gets drawn into the cylinder, and the dispacement of that cylinder is 1.2 liters, the total efficiency is 1/1.2 (or about 83%). At 0 RPM and 100% throttle (well, any throttle position that isn't completely closed), volumetric efficiency is always 100%. But as the engine starts turning (at full throttle, otherwise the vacuum drawn by the throttle restriction will reduce efficiency), the actual efficiency will depend on intake design. Considering that OTTO cycle engines use valves, air is only drawn in 25% (about) of the time. So the vacuum drawn trying to draw that air in will cause the efficiency to drop. However, intake runners are designed for this. So basically, when the valve closes, the momentum of the air causes a pressure build up behind the valve. That pressure will cause the air to reverse direction. This leads to a harmonic wave in the intake runner. The frequency of the wave is dependent on the design of the intake runner (cross-sectional area, cylinder volume and length mainly, but curves and other obstructions do play a part). If the valve opening is timed properly with this frequency, the incoming pressure wave from the harmonic will actually force air into the cylinder. That's how some racing engines can actually achieve a higher than unity volumetric efficiency at a specific RPM. It's all relative to the design of the engine. Some engines may be designed for 2000 rpm. And increasing the RPM over that WILL decrease VE. But you cannot say as a general rule that VE is inversely proportional to RPM, because it isn't. And pumping losses are directly proportional to VE (in fact, the pumping losses are DUE to VE below 100%).

You do have a point that thermal and mechanical losses do increase with RPM (Mechanical due to friction, thermal due to the increased movement of air around the parts). However, your reasoning behind diesels being more previlent is flawed. It's not because they operate at a lower RPM. It's because of a few reasons. First off, diesel is denser (energy/volume) than Gasoline while still having a similar stoichiometric ratio with air. Secondly, diesels are typically built without a throttle blade. That means that even at idle or lower power settings, there is no restrictive plate to draw a vacuum (and hence harm VE). Since diesel doesn't behave as bad as gasoline when run lean, they typically control power output by controlling the fuel flow. Third, diesel engines tend to burn much hotter than gas engines (the flame front is significantly hotter), so there is a more complete burn. You combine these effects, and you can see why they are more efficient (and it's not because they run slower). The reason that diesel engines typically run "slower" is two fold. First, since diesel engines don't use spark plugs, timing is controlled by the mechanical fuel injectors (direct injection). They were simply not fast and accurate enough to time at high rpm. The second reason, is that diesel is slower burning than gasoline. So at higher RPMs, there's a large chance that combustion won't be complete when the exhaust stroke starts (resulting is a large drop in efficiency and a large increase in mechanical stress).

It would seem to me that this is an ideal application for a (diesel) turbine engine. A turbine has very consistent RPM/torque output: this is why, despite its efficiency, they have not been used in vehicles with any regularity.

If you could "seamlessly clutch" from "stopped" to full speed, back to "stopped" and then into reverse all while remaining at a consistent, low RPM, you'd have the perfect transmission for a diesel turbine. Very exciting! We might be able to significantly increase the petroleum effici

The Prius uses a single torque differential. This uses a pair of them reversed onto each other. The "output" on the Prius is the input on this. The two "inputs" relate to the two shafts. The unique thing about this is that it uses the two shafts and the relative motion between them to control the output speed. So while it uses some similar parts, the theory of operation is completely different. Just because it uses a planetary gear set, doesn't mean it's the same...

No, Toyota brought it to market first. The so called "power split" electric CVT was first described in a 1971 paper by some guys from TRW. It's an American invention. And yes, this guy is just doing a much more complex version of it. There is only discussion of speeds - all he's really got is a way overcomplicated differential. Once he looks at how power flows through it, he'll be very disappointed. It's a big nothing.

By "frictionless" I assume they're talking about something to do with the clutch, where you have two plates that you can jam against each other to transmit power via friction (and if you take them a little distance apart you they have a little bit of slip to them, so that during a gear change can the engine's speed will be smoothly met by the friction until it matches the drive-shaft's speed without any terrible lurch which would damage everything). This thing still has normal mechanical friction, as any set of gears would, but doesn't have any component explicitly designed for friction.

They are actually comparing it to other times of CVTs, which use friction belts driving a pair of cones. Nothing to do with the clutch. The device from TFA uses only gears, in particular a set of planetary gears, so they say that the advantage would be no danger of slippage compared to friction driven CVTs. From what I know, in the usual designs, the slippage problem is not really limiting anyway, though.

Slippage limits torque. the whole advantage of this system is that it allows infinitely variable output - from full speed reverse through neutral, to full speed forward, all with full torque limited only by the size of the toothed gears used. All power transmission in this device happens through toothed gears. There are no belts, friction plates, clutches, etc - all toothed gears and only toothed gears, with zero slippage, full torque, and infinitely variable output .

Yeah, but that's basically the working principle of any planetary gear system. If you don't hold any of the components locked in a planetary gear, you can configure the output to be proportional to the ration of the inputs. Combine a CVT with a planetary, and you get an infinitely variable transmission. That's used in hybrid vehicles all the time, and doable with gears only, not using friction components. From quickly skimming over the video, I definitely see a planetary gear setup there. As I said above, I'd love to see more technical detail on that one, TFA does not really make clear what is actually new about this.

The new aspect is that this planetary gearset actually has TWO inputs, and the output is determined by the *difference* in speeds between the two. That's how it can go from reverse to forward seamlessly. V1 > V2 is Forward, V1 V2 is Reverse, V1 = V2 is Neutral. Assuming there are no practical limits on the velocity of either input, the possible difference between them is infinite.

Personally I find this really exciting, because i've always been in love with the idea of a variable transmission. Ignoring electric motors for a minute, there are some absolutely INSANE things you can do to a small motor with cams, turbocharging, etc, to extract absolutely massive amounts of power from teeny engines. Like, 1000+hp from sub 2 litre motors. The problem is they end up being extremely peaky (power is only made at a narrow RPM band, or a terribly high one)... but with a variable transmission you can let the engine hunker down in it's sweet spot and let the tranny worry about all the fiddly bits. Hell, you can even do the same thing with a big engine... I wonder if its possible to make five figures of power from a 7 litre? With this we just might find out.

The new aspect is that this planetary gearset actually has TWO inputs, and the output is determined by the *difference* in speeds between the two.

You just stated the definition of a differential gear. It is not new in any way, and describes exactly how a planetary gear works and is normally used. For a real world example take a look at the Hybrid Synergy Drive [wikipedia.org] used in Toyota Prius. It has precisely that: A planetary gear with two inputs summing up to one output, allowing the engine to operate at optimal rpm regardless of wheel speed.

Not at all. This device has three inputs, GP neglected to mention the main engine. It uses two smaller inputs to affect the main larger input. The prius balances two engines of rougly equal size. This controls a single engine with two much smaller ones. It seems to be a novel and unique transmission.

Whether you add two or three power flows makes little difference to the principle of operation. You do not escape the fact that the "control" engine(s) will be experiencing a proportional amount of torque as the main one.

It seems to be a novel and unique transmission.

Well, many things seem novel and unique when you lack the relevant expertise.

I did watch video in TFA, and it doesn't make it clear how this device works. It does suggest, however, that they haven't actually made any real measurements yet, so whether it works as they think remains to be seen. Regardless, what I instantly dismissed was the GGP's claim that combining two inputs to an output is anything new.

It's quite different from the HSD in that it has three inputs, contrary to what GP said - one power input, and two control inputs, both of which ought to require just a fraction of the input power to control the input/output gear ratio.

"The torque provided by the Control shaft will typically be of the same magnitude as the torque provided by the Input shaft."

"The Control shaft (and associated mechanical elements) should be sized to this torque requirementaccordingly – the Input and Control should be considered as parallel power paths rather than as ‘power’and a ‘control’ elements respectively."

So this whole thing isn't very useful. To add this as a transmission to a power motor, you needone ore two additional motors of same power with variable speed and enough torque at any speed.

I hope you're not saying what I think you're saying. Transmissions CAN'T increase horsepower. All they do is keep the engine from stalling by trading speed for torque. Horsepower is rotational speed X torque so the total horsepower doesn't change just the ratio of torque to rotational speed.

I think the transmission design is very cool and I'm amazed that someone can still come up with new ways to combine gears that haven't been done before. In fact, there was a post claiming someone had come up with a s

Not really new. Model T's had differentials. And why are differentials called that? Because they "difference", as in subtraction, rather like Babbage's difference engine. All this thing is doing is distributing the speeds of 3 shafts so any 2 add up to the speed of the other. The wonder is that apparently no one has applied this idea in a transmission. Maybe that's because there's some fundamental problem, like, oh, how to drive 2 shafts so that the 3rd one can be precisely controlled? I suspect the electric motor used to drive the 2nd shaft may need to be so powerful that this idea may prove impractical. The inventor tries to get around that problem by having that electric motor act more as a brake, always running at negative rpm, so to speak. Notice that "top gear" is the 2nd shaft being locked to a speed of 0 rpm. The 2nd shaft could be run forward for an even taller top, but that would take real power, so this invention doesn't do that. We can hope that it works.

Perhaps most people on Slashdot have never played around with a differential? Jack up the rear wheels of a manual transmission, rear wheel drive car, and see what happens when you spin one wheel by hand. If the transmission is in gear (engine off, of course), the other rear wheel will spin the opposite direction, at the same speed. If the transmission is in neutral, the opposite wheel and the drive shaft will spin at some rate that together adds up to the speed you're spinning. Usually, the drive shaft will spin and the opposite wheel won't, because the wheel has the greater mass and inertia.

Also perhaps most people here have never had the experience of getting one rear wheel of such a car on extremely slippery ice? I'm talking ice right at 0 C, with water on top. (Well, if that's what road conditions are like, just stay home that day.) You might think you're okay if at least one wheel can get traction. Nope! If your vehicle doesn't have differential lock, you're stuck. The one wheel on a dry surface won't move, while the one on ice spins twice as fast.

Can you elaborate? You say "combine a CVT with a planetary...not using friction components" but I was under the impression that a standard CVT (with 2 cones and a belt? That's the kind I know about) does use friction components, whereas this new design doesn't.

What I don't get is how exactly this is distinct from a differential gear.

Yes. That's basically what the Prius does: it uses a differential (actually an epicyclic, which is a flattened differential) as a mixer, and drives one input with a gas engine and the other with an electric motor, giving not only an infinite number of speeds but also a way to use the engine to charge the motor with excess power, or use the motor for braking. But then you need both an engine and a motor. Managing an infinite drive from a single input is pretty cool.

It is a very interesting approach, the problem that may happen (I don't know, just guessing here) is to locking the lower shaft while trying to go full force, isn't the entire premise of friction basically shifted (sorry for the pun) to the device that will stop or let go of the lower shaft, which needs to be stopped for the torque to be transmitted to the wheels for example? So there are these 2 small black gears if you look at the video, these gears are perpendicular to the lower shaft, sitting on it sid

isn't the entire premise of friction basically shifted (sorry for the pun) to the device that will stop or let go of the lower shaft, which needs to be stopped for the torque to be transmitted to the wheels for example?

I'm no engineer either, but AFAICS the two counter-rotating shafts share the load between them, and the forward/reverse motion is the difference of the two.

So if one shaft is strong enough to transmit full torque from input to output, there's no problem if you split it between them because

Not to worry about 'infinite' or 'frictionless' - these characterizations are not the intent of the device so we can just evaluate it as a normal continuous transmission being controlled by the ratio of speeds between a control shaft and the drive shaft. Efficiency for low-torque cases can be quite decent as eccentric bearings, gear-qualities and diameters can be controlled well with current techniques.

So... with a real torque, there will definitely be significant forces between the two shafts. Clearly, the full torque will be on the central, driving shaft, while some smaller fraction will be on the upper shaft. As we bring the distance between them down, then the torque between them can decrease, but then there will be more stress on the smaller pinions' teeth. Planetary gears are great for this class of problem and he's throwing decent diameter eccentric bearings in where he can too. The bloke seems honest, and has clearly thrown a fair amount of time and energy into the problem.
There are other approaches to controlling gear ratio via the speed differences between two shafts - he's not trying to do something impossible, he's just trying to do something difficult, successfully. Whether the cost of the bearings and gearing will be favourable when compared to the other approaches is the question. I think his system will work - and decent sealed bearings, high strength pinions, planetary systems - these already exist and are stable tech in current transmissions, even in relatively dirty industrial environments where the transmissions aren't as protected as in cars. In particular, the cost of electronic control for motors has fallen massively over the last years, so if nothing else, the general class of solutions using differential speeds of low-torque motors to control a high-torque transmission is more appealing now.

The real icing on the cake is (as mentioned near the end) the secondary drive doesn't require a whole lot of power so it can be run by a flywheel

This is something that bothers me as I look at this demo. The secondary drive doesn't require a whole lot of power, because there is literally nothing attached to the output to counteract the little motor's selected ratio.

To simulate the forces of what it'd be to have a car attached on the output, you can just use your hand and try to hold the output from moving, while the ratio is not in neutral. If there is a weaker motor and a stronger motor, what do you think will happen? The stronger motor may feel a pinch, and the small motor will be completely unable to stop the output from distorting the ratios, making the entire setup unusable.

Now, I hope I'm wrong, but there better be something hidden from view That Changes Everything.

If this gearbox works we could see a massive decrease in fuel consumption and much better power delivery in our cars.Because right now the gearboxes are rubbish, they haven't evolved much in the last decades.

Your Prius's CVT has limited torque because your CVT uses power transfer mechanisms other than toothed gears alone. The D-drive uses toothed gears only, not belts, not friction plates, etc. This allows for more torque than other CVT designs.

The way I understood it (could be wrong), the Prius drive is only one half of what this guy came up with. The clever bit is the other half. The Prius transmission would not work well without significant torque input/output(electric breaking) on the electric side. The way this works, there is almost no load on the ratio selection element, the only input it needs is enough to create a difference in speed.

Actually electric motors have a pretty good efficiency over a wide range of power levels. It is ICEs that have a small band of optimal efficiency around a certain rotational speed. So, conventional combustion engines do profit most from this. Besides, electric motors have a rather flat torque curve, so you usually do not need a gearbox for them at all.

Reality is exactly opposite. Induction motors are very efficient through most of their operating range, while internal combustion is really only efficient along a narrow band of RPM, which is typically optimized to be highway cruise speed in high gear. With induction motors, they would merely allow for a much simpler controller, one that does not have to provide variable frequency power output.

That's not entirely true. Dr. Porsche a really long time ago more or less solved that problem. By inventing a vehicle that was propelled by an electric engine but powered by a gas one. Meaning that at all times the gas engine was working at it's most efficient gear ratio, but since the electric engine was driving the actual wheels it could be very efficient and give just the power needed at any given time.

Right, that's called 'gas-electric', or 'diesel-electric', or 'turbo-electric', or if you want to associate a good design like that with an abomination, 'series hybrid'. It has been used in production for decades on locomotives, and is becoming more common on ocean vessels. There are even a couple vehicles using such a configuration.

The problem is that the speed of induction motors is relative to the frequency they are being driven at. It requires some complex circuitry to provide high power at a variabl

Turbine without regeneration cycle have approx 30% efficiency and can up 40% efficiency if hot exhaust is returned into the cycle (regeneration). Diesel piston engines actually achieve between 40% and 45% efficiency at optimal constant speed. If you consider turbine systems at optimum efficiency with regeneration and high operating speed are quite large, noisy and need tight maintenance cycles for the finely adjusted and physically resistant blades, this is not suitable for small vehicles. By the way this n

Another type of engine that really likes to run at a constant speed are gas engines (primarily methane or propane). This sort of equipment would be a huge benefit to the natural gas industry as it would allow variable speed compression while the driving engine runs at a constant speed. Currently you have to put a generator and a variable speed electrical drive in between the driver motor and the compressor.

Assuming 1000 miles per month (which is what most leased cars are allocated) :The difference between a 150mpg car and a 250mpg car is 32 gallons of gas per year per car.The difference between a 30mpg car and a 40mpg car is 100 gallons of gas per year per car.The difference between a 20mpg car and a 30mpg car is 200 gallons of gas per year per car.The difference between a 15mpg car and a 25mpg car is 320 gallons of gas per year per car.The difference between a 12mpg car and a 22mpg car is 450 gallons of gas per year per car.The difference between a 10mpg car and a 20mpg car is 600 gallons of gas per year per car.

Read from bottom up, you see the point of diminishing returns.

If car companies would focus on the right range (forget about exotic expensive 150+ mpg carbon fiber hybrids that hold two people, focus on 30+mpg vehicles that hold a family and gear) they would have a LOT more impact. I don't necessarily agree with the way cash for clunkers was handled, but in the cases where people traded in a 12 mpg car and drove off in a 22mpg car - it makes a BIG difference.

Unless you consider the negative environmental impact of disposing/recycling all those used cars and the manufacture of newer ones. We would have done less damage to the planet by forcing everyone to drive the car they had an additional year before they could buy a new one.

And thats completely ignoring the fact that the fuel saved by cash for clunkers was only about 1/5th the cost of the program.

If I had traded in my 18mpg Oldsmobile for a 30mpg car, I would have only saved about 250gallons a year. At 3 per

At 3 per gallon, that only saved me $750 dollars. How much of my tax money did the government spend on it though? Oops.

Fortunately for supporters of the program, the goal wasn't just to save you money on gas. That new car also resulted in a bunch of taxes for the government, in that auto workers were employed and getting taxed on their income. And still buying stuff, resulting in more taxes and employment, and then those people bought stuff (and so on, and so on)

Yeah. Why would anyone drive a stick when it means they can't talk on their cell phone, put on their makeup and stuff a big mac into their faces at the same time? Sheesh....and before anyone says it, yes, I have seen people talk on their phones or eat or put makeup on while driving a stick. Just not all three at once.

My car as 110,000 miles on it. I've raced my car a good bit (legal track racing, of course).

The first clutch (stock) I destroyed was by adding a 150hp NOS system on.
The second clutch (performance) was destroyed by my ex-wife driving it uphill and she slipped the clutch the whole way (like 5 miles). She obviously wasn't very good with a stick.
The third clutch (performance) was actually from old age.

My friend has a comparable car. It's the same engine, transmission, body style and weight. She drives more normally than I do (no racing, just city/highway driving). She had her clutch changed at 100k miles. Labor to replace the clutch is about $350 to $500. Parts are about $150. This car happens to be a bastard to work on, which is why the labor is high. So, $500 to $650 for the job.

This is about the age that an automatic transmission would need to be rebuilt. For this car equipped with an automatic, removal, rebuild, and replace costs about $3,500.

So, with my car, I've improved the efficiency by helping the airflow out (one minor exhaust fix, and a some intake fixing). I enjoy cruising at highway speeds with low RPM's (6 speed). The same car with an automatic would be cruising at a much higher RPM (4 speed), and suffering from losses related to the automatic transmission.

I rarely need to check my transmission fluid (i.e., gear oil). If my gear oil runs low, it could increase wear. A car with an automatic has to have their transmission filter and fluid changed. If their fluid runs low, it can be catastrophic.

There's about a 300 pound difference between the manual 6 speed and the automatic 4 speed.

I can drive pretty much anything with wheels, and I've proven it. I'm licensed for motorcycles and cars. I've also driven everything including a big truck with a 10 speed air shifter. a neighbor bought a motorcycle, but didn't really know how to drive it. They told me it wasn't driving right, so I grabbed my helmet from the garage (I don't have a bike right now, but I still have the helmet), and took it for a spin. It worked fine. It was operator failure.

While quite elegant, this solution requires power input... So not so great on a bicycle...

And as far as cars go, you have to spin a shaft in order to achieve neutral. Which means that you still need a clutch or something for a car to be safe. (If the engine's running and the electric motor spinning the shaft fails the car will go forward... Not nice.)

(Am I the only one who thought that the TFA's statement that understanding these mechanics is dumbing it down? I think it's simple, honestly. I'm not claiming I would have invented it, but I do understand the principle...)

The greatest limitation on today's CVTs is the lack of sufficiently strong materials for the belts. While research and development has already yielded marketable CVTs, they are limited to being paired with relatively low displacement, low horsepower, low torque engines for durability purposes. Your father's Oldsmobile's honkin' huge Rocket V-8 or your cousin Bubba's new pickup truck's V-10 would likely tear any of those CVT belts to shreds. Supposing that this new design is strong enough, those engine pairing limitations could be done away with once and for all.

Several tractors I have owned have hydrostatic transmissions. These are also infinitely variable, but they use a hydraulic pump and motor to achieve it. They provide very high torque and excellent power transmission. I always wondered why they were never used in cars.

Fluid friction losses. Recirculating a fluid via a pump in a closed system actually makes a bit of heat, especially when there's a bit of load on it. Works great when something can be built big and doesn't need to go very fast (like the tractor application you mentioned, also used a lot in earth moving equipment and fork-lifts), but when having something that goes fast - not so much. Also if you go too fast, you're either going to have some kind of undesirable hammering or cavitation at a certain point depending on what kind of pump you use to provide hydraulic power.

Some air motors use a tilt-block that does something similar as well in regards to infinite variable speeds, but they're not so much about efficiency as about being able to control speed in industrial environments where electric motors aren't always desired. (Like working around water or in a no-spark environment.)

It's loud. Plus you have to have a heavy hydraulic system (pump, oil reservoir, valving, etc). In practice an electric motor gives you most of the same benefits of a hydrostatic system, but it's a lot lighter and doesn't require an oil system. Of course batteries are heavy, but aren't strictly needed (as in a locomotive).

A few years ago I heard of a design that used small hydraulic motors connected to each car wheel via clutches that would efficiently overcome the propensity of a differential to send power where you don't need it. Basically when slippage was detected, the clutches would engage and the faster wheel would act as a pump, sending fluid to drive the other wheel. The beauty was that if you tied all four wheels into the same system, you could get on-demand four wheel drive as well.

Another prototype I heard of used a hydrostatic system to charge up a nitrogen accumulator in a form of regenerative braking system.

Hydrostatics also has limitations in the amount of power you can transmit. Every large combine harvester we've ever owned has had a hydrostatic transmission, but no tractor ever has had. Combines typically don't pull things; driving power is minimal compared to the power consumed by threshing. Whereas in a tractor, it's all about driving power (outside of PTO applications). You just can't really put 500 HP of pulling power through hydrostatics. Most hydraulic motors are gear motors, which means the oil spins little gears. Under high load, oil slips past the gears without turning them. Compare that to electric where on a daily basis Locomotives pass thousands of horsepower from big diesel engines to the wheels with electric motors.

They were used in cars, back in the '60's. The actual name of the transmission escapes me right now, but they came in both mechanical and hydraulic flavors. One gave you more torque, the other more power. Bah, and I'm sure they weren't called hydrostatic, but they could do exactly the same things. GM put them on their super-blocks.

I think the weakness in this design is the need to rotate the "bottom" shaft at a speed equal to the input shaft for neutral. While indeed it doesn't need a lot of power, it's a lot of rotation where, in competing designs, a clutch disengages or the drive motor is idling. I could see a lot of things going wrong if the synchronization was imperfect, or if something went wrong.

How do you start this up from a dead stop? Somehow you have to exactly match the shaft rotation speeds to keep it in neutral before you start moving forward, otherwise there will be a lurch.

I look forward to seeing how this is developed further. It has a lot of potential.

The big issue in science and engineering is ALWAYS reduction to practice. The inventor acknowledges this and is working with an engineering firm to make a practical pseudo-production testing model. When you have no clutches, the lack of shock loading means the size of gears and the housing can be substantially reduced, since there won't be an engine load shock issue. There can be issues of loads when parked, though, when another car bumps yours. The other issue is how do you tow such a car when the engine fails or you want to tow it behind a motor home? There may still need to be a "cog" connection for towing.

Issues involved in getting it into a small, produceable and cost effective prototype will tax the engineers. If they can do it, there will be applications in many different fields.

Given that the gear ration can be set by controlling the small electric motor speed, it can be integrated with other electronic control systems easily.

I have to hand it to the guy for coming up with a very clever implementation. This is why we need to support the math, science and physics departments everywhere, because in the end, the world is a physical place and the countries who prosper the most will be the ones with the most technologically up-to-date innovators.

For every action, there is an equal an opposite reaction. So, when your monster torque motor is spinning the input shaft, surely it is pushing against the counterspinning shafts with exactly that amount of power? In other words - won't the mechanism (electric motor, flywheel, etc.) that keeps the counterspinning shafts running at the desired speed ratios have to overcome this reaction? It's possible that the frictional and mass inertia of the system helps some, but how much?

I'm not an ME, but the explanation of what the required control motor power is relative to input motor power is very thin here. Be very interesting to see what the detailed input / output / control torque & power measurements end up being.

His next phase prototype should have a 10-20 HP IC engine (lawn tractor motor, etc.) for the prime mover, and the output shaft of his device needs to be connected to a dynamometer/load absorber of some type.

Can he still control it with the small DC permag gearmotor he appears to be using?

At first blush, I'd say that both Toyota and John Deere have already produced something similar. What he appears to have, however, is a system that can smoothly transition (with power) through neutral and reverse. That indeed could be the cool, patented part, as the rest of his transmission is pretty well understood and actually in production already in many of the applications they list for their invention. I don't see any patent application listed, so I can't tell for sure exactly where his breakthrough is.

Here's the fundamental principle by which his transmission works, though: Basically the idea is you supply driving power to a planetary gear system and then use another variable system such as an electronic motor or, in John Deere's case, a hydraulic motor, to take speed (but not power) away from the output shaft by spinning part of the planetary system. If you understand how a planetary gearbox works, this makes sense. So in John Deere's case, the less-efficient hydraulic motor uses a tiny amount of power to control how the actual, geared, power is transmitted to the wheels. Using this system JD has a completely variable system with a particular gear range (this is a tractor after all) that has a powered neutral stop. In the pictures and video you'll note he has two electric motors that control the ratio.

Toyota does something similar with their hybrids, although it's more of a way to efficiently (and brilliantly, I might add) blend the gasoline motor's power with the electric system in an infinitely variable way.

Another way of implementing an IVT, though I don't think it is as efficient, is to use a differential. Power comes in the normal part of the differential (IE spinning the entire gear assembly), and then power comes out one side, and an electric or hydraulic motor attached to the other side (Where the wheels would normally go). You can then use the motor to change the apparent gear ratio, and even reverse it.

Hate to reply to my own post, but here is a fairly detailed explanation of John Deere's IVT: http://salesmanual.deere.com/sales/salesmanual/en_NA/tractors/2006/feature/transmissions/8030_option_code_1127_1137_ivt_trans.html [deere.com] . The relevant part is "The John Deere IVT uses a hydromechanical, power-splitting design where a portion of the power is transmitted mechanically and a portion hydrostatically. A hydromechanical transmission is more efficient than a purely hydrostatic transmission because gears carry power more efficiently than a hydraulic pump and motor. By careful selection of the gearing, the John Deere IVT carries a maximum of the power mechanically both at normal field working speeds and at transport speeds, taking maximum advantage of the higher mechanical efficiency while providing the control and versatility of a hydrostatic." And of course this power-splitting is done via a planetary gear system.

I say this not to take away from the D-Drive's awesomeness (John Deere doesn't do reverse without shifting a gear), but to help offer explanations of how it actually works.

The Thompson coupling [youtube.com] was invented not long ago, and I remember being amazed that there was anything new to be done in the area of mechanical power transmission. And now this. Are we all done now, or is there more still?

Well this D-Drive resembles the Thompson coupling in that they both seem new but they're really not. The Thomson coupling is a (admittedly nicely packaged) double cardan joint, while the D-Drive is a powered-planetary, already used in infinitely variable transmissions before. I'm not sure if that particular arrangement existed before, and it's nice to see that novelty is still possible in basic mechanics, but similar devices with powered neutral already exist (for example in tractors).

I watched with interest through 3/4 of the video as they continuously refused to show the back side of the model, just loosely discussing the "control shafts" and couldn't get it out of my mind"pay no attention to the man behind the curtain".

Then finally at the end they showed the back and surprise, there's another motor there, but trying to explain it off that this motor requires far less energy than you're going to gain by using the rest of the system. Maybe this is true, but that's a poor way to present the design, by hiding a serious concern until the last second.

As they wrapped up the video they did admit that this little kink is going to be the determining factor in whether or not it's a useful design. "Why can't they just tap some of the power off the input shaft to manage the control rods?" I thought. Then it occurred to me, the speed would need to be continuously variable, and that's the whole problem they're trying to solve. So, what we have here is a continuously variable mechanism, so long as we can already provide a continuously variable mechanism. (all his D-Drive needs to complete it is, another D-Drive, which would of course need another D-Drive....) Sounds terribly recursive to me. But he didn't go into any detail as to the requirements of this control system, but from what I can tell, it needs to be continuously variable also. He dismissed it as being easy to achieve with something such as an electric motor, which one could argue the same is true of his entire invention...

We'll see. I'll remain skeptical until his design is complete, including the nagging little details of running the control shafts. But really it's an excellent idea even with this problem. It's solved the larger portion of the problem. One other thing that also came to mind is balance. The orbital gears could really get whipping around the sun gear, they'll have to be balanced. Using orbital gears itself at high torque will create new problems also. I'm no mechanical engineer but I also see a potential problem there with torque on the position of the planetary gears since the shaft isn't fixed. You don't usually see floating gears in transmissions.

Then finally at the end they showed the back and surprise, there's another motor there

They mention the electric motor 2 minutes in, and they constantly talk about driving the bottom shaft, implying you are providing some sort of power input. They didn't show the back of the device for a while because looking at an electric motor is less helpful than seeing the output when trying to understand how the thing works.

As they wrapped up the video they did admit that this little kink is going to be the determining factor in whether or not it's a useful design

They spent most of the video trying to explain how the device works, so understandably they get to the application stuff only at the end. He just showed the device working perfectly fine with an electric motor- you don't need to work out a continuously variable input from the main motor unless you really want to. As for the efficiency, the input power is exactly the main concern, but it sounds perfectly plausible for this input to require minimal power. As they mention, the electric motor isn't seeing any of the main motor's power, so the required power for it can be very small.

I agree vibration issues and robustness have yet to be seen, but the device is simple enough it should be feasible. Engineering this from a demo to a working transmission for a full-size motor can be as much work as developing it in the first place, so it may be a while before we see where this goes.

The largest value of this device is in its "wow, how does that thing work?" design. By baffling the onlooker and also describing the widget very carefully the illusion of a wonderfully useful device can be created.

It has a problem in the real world, though. The reaction torque is equal to the working torque - and the reaction torque path runs through that "secondary control shaft." This will become obvious as soon as he tries to transmit some significant power through his device. What he's showing isn't a new invention at all, it's just a mechanical "summer" that adds the inputs from two input shafts. All that's new here is some fancy handwaving and creative description.

It might be good enough to fool some people but Mother Nature and those who paid attention in school aren't fooled. Maybe if / when he actually tries to transmit some power through his "invention" and the control motor just spins backwards he'll "discover" a source of electrical energy?

- and the reaction torque path runs through that "secondary control shaft."

If either were the case, then as the secondary motor spun up either the drive motor would have to slow down or the total speed of the two drive shafts would change.

The drive motor never changes speed, and neither does the total speed of the two drive shafts.

In your scenario, the top shaft would not slow down as the bottom shaft sped up, it would simply keep spinning at the same speed. To get the system in neutral, the control shaft (and therefore the control motor that drives it) would have to spin at the same speed as the drive motor and shaft. In order to make the output shaft spin in reverse, the control motor would have to be twice the size of the drive motor!

That is obviously not what is happening, so now you have to look at what is happening. The control motor is spinning the planetary gears around the drive motor's ring gear and the output shaft's ring gear, effectively neutering all the torque the drive motor is applying. This is exactly the same as applying a clutch, without needing two friction plates - just a spinning motor and some planetary gears. When the control motor spins faster, the effect is to reverse the direction that the planetary gears need to spin to compensate for the torque being applied by the drive motor.

The only things the control motor is applying any power to are the planetary gears, and then only to affect their relationship to each other. It is completely isolated from the torque conversion loop, even though it looks like it is right in the middle of it. When the control motor is spinning at full speed (reverse), all of the power is still being supplied by the drive motor. You could swap out a bigger motor on the drive side and apply a load on the output side and the results would be identical. So long as the RPMs didn't change with the larger motor you wouldn't have to change any gearing on the control motor or any of the planetary gears.

So you think the reaction torque is different than the working torque? Do you even understand the definition of torque? Torque is the effective radius multiplied by the force. Your reaction shaft might be geared lower so that it doesn't require as much force to push, but its the lower gear has a smaller effective radius. These two things negate each other and you still end up with the same torque. The only difference is the speed of your output. A higher output RPM is balanced by the reduced force whi

A lot of the replies bring up problems of going completely with this solution (how do you get it started if you need things spinning first, how do you tow a car with one of these). Admittedly not an optimal solution, but a very effective one could be to still have a clutch in the mix for some of these situations. Considering that the clutch would only be used fairly rarely, and could be engaged while the rest of the system is in neutral (meaning it's fairly low engagement load), it could be much smaller and have a much longer life than the typical clutch arrangement.

Clutches don't have to have a short life. The clutch in one of my cars that I've owned since 20 miles now has just under 200K miles on it. I've been expecting to have to replace it for a decade. But, the way I drive it seems to pamper the clutch.

the speed of those 2 shafts is what controls both the output speed of the device and direction of rotation.
The control over speed and direction is independent of the power input.
How did you think that was manipulated? Mind Control?

The con is the statement that the control shaft will require very little power to operate. If you stop the input shaft, you can see that the control shaft works the same as the planetary gear system on many commercial devices, like a cordless drill. I don't know about you, but the planetary drive on my cordless drill doesn't prevent me from going through batteries when I'm doing something heavy like using a hole saw. Given that, at times, the control shaft will require no less power than the input shaft, you would need a way to provide high power at variable speed. Therefore, you would need a CVT to operate your CVT.

My other concern is the gear tooth size. A traditional transmission uses gears that are quite large and have few teeth. The D-Drive has gear teeth with at least two orders of magnitude smaller teeth in critical places, and they are at a smaller radius. I think this thing will need to be huge to transmit enough power to move a vehicle. Large radius gears are necessary to transmit a lot of power. The planetary design of the D-Drive does not permit large radius gears.

I agree, it sure looks like the output torque is generated by pushing against the control drive motor, meaning that maximum torque at ratios less than 1:1 is related to the rating of the control drive system.

The control system has the smaller central gear, so there will be some mechanical advantage that will "step up" the torque the control system can provide, allowing for a smaller control powerplant.

He mentions a kinetic recovery system to power it, which to me indicates an intention for intermittent us

Or more specifically: Whatever's driving the control-axle will be fighting whatever's driving the main axle, so it has to be as powerful as the main motor. In which case, why not just use that in the first place?

Actually he says it does not act against the control axle. It only needs enough torque to defeat gravity resisting that metal ring gears weight.

A tiny radio controlled car motor can clearly be driven to fast speeds at enough torque to defeat gravity resisting the car from moving, which arguably will weight more than a metal gear piece at this small scale.

And at larger scales with heavier gears and parts, you just scale the small motor up too.

Yes, the behavior of this "transmission" should look familiar to anyone who has ever played with a differential while experimenting with Lego gears.

With a classic differential (the piece pictured here: http://en.wikipedia.org/wiki/Differential_(mechanics) [wikipedia.org] ), there are four different things rotating, and their speeds are related. The equation is something like (A-B) = (C-D). The problem is that one of these rotating things is very hard to access mechanically - the inner bevel gear, whose axis of rotation mov

I agree, the motors are not torquing against each other, that would be very inefficient.

But the control motor will be be subjected to torques related to propelling the vehicle. It doesn't just "turn the gear".

Example: Let's say the control shaft is rotating at a rate r. When the control shaft rotates faster, at rate 2r, that would be a higher gear (in other words, the output shaft would have higher speed and lower torque than the input shaft). If it's rotating at rate r/2, that would be an easier gear.